The president regularly flies in helicopters call sign Marine One operated by the U. Seven planes or more often accompany Air Force One with all the extra agents, journalists, weapons, cargo, and other items needed for the trip. Tillman explained that this was due to his concern that because of the reported threat, Air Force One would be attacked when he returned to Andrews Air Force Base. The Guess Where II was used to transport senior members of the Roosevelt administration on various trips. Air Force One is capable of refueling midair, unlike commercial jetliners who carry a fixed fuel and have to land for refueling. Sitting presidents have been flying for less than a century. The National Security Act of , the legislation that created the U. The Air Force One is one of the most recognizable symbols of the presidency, and probably as important as the White House itself, where the Commander-in-Chief resides when on land.